High‐Performance, Transparent Thin Film Hydrogen Gas Sensor Using 2D Electron Gas at Interface of Oxide Thin Film Heterostructure Grown by Atomic Layer Deposition

Abstract

A high-performance, transparent, and extremely thin (<15 nm) hydrogen (H 2 ) gas sensor is developed using 2D electron gas (2DEG) at the interface of an Al 2 O 3 /TiO 2 thin film heterostructure grown by atomic layer deposition (ALD), without using an epitaxial layer or a single crystalline substrate. Palladium nanoparticles (≈2 nm in thickness) are used on the surface of the Al 2 O 3 /TiO 2 thin film heterostructure to detect H 2 . This extremely thin gas sensor can be fabricated on general substrates such as a quartz, enabling its practical application. Interestingly, the electron density of the Al 2 O 3 /TiO 2 thin film heterostructure can be tailored using ALD process temperature in contrast to 2DEG at the epitaxial interfaces of the oxide heterostructures such as LaAlO 3 / SrTiO 3 . This tunability provides the optimal electron density for H 2 detection. The Pd/Al 2 O 3 /TiO 2 sensor detects H 2 gas quickly with a short response time of <30 s at 300 K which outperforms conventional H 2 gas sensors, indicating that heating modules are not required for the rapid detection of H 2 . A wide bandgap (>3.2 eV) with the extremely thin film thickness allows for a transparent sensor (transmittance of 83% in the visible spectrum) and this fabrication scheme enables the development of flexible gas sensors.

Recent advances in mechanism investigation of atomic layer deposition by &lt;italic&gt;in situ&lt;/italic&gt; photoelectron spectroscopy

“…目前, ALD技术已在 微电子领域得到了广泛应用, 包括用于制备微处理器 中的晶体管栅介电层 [ 5 ] 、集成电路中的互连籽晶 层 [5] 、动态随机存储器(DRAM)和3D NAND器件结 构中的介电层等 [6,7] . 同时, ALD技术也被广泛应用于 微纳机电系统 [5,8] 、显示与发光 [5,9,10] 、光伏 [11~13] 、能 源存储 [14~18] 、催化与电催化 [19~23] 、传感器 [24,25] 、表 面防腐 [5,26,27] 、太空防护 [28] 以及药物缓释 [29] ; ALD沉积薄 膜的厚度由周期数精确控制, 因此可从原子尺度精确 控制薄膜的厚度; ALD生长温度一般较低(室温至 400℃), 可用于在温度敏感的基底材料(如有机材料) 上沉积薄膜 [24] ; ALD沉积薄膜的重复性好, 适用于大 面积薄膜的制备.…”

Harnessing Conductive Oxide Interfaces for Resistive Random-Access Memories

“…Later work has demonstrated that 2DEGs can be formed at more simple interfaces, between amorphous and single-crystalline oxides [30,31] with the benefit of room temperature preparation. Recently 2DEGs were shown to form even at amorphous/polycrystalline oxide interfaces [17,21,32,33] (Figure 1C). Furthermore, the oxide deposition temperatures were reduced from 650-900 °C to 25-300 °C, and the deposition techniques have been extended from PLD to the more scalable atomic layer deposition (ALD), which is widely used by the microelectronics industry.…”

“…These oxide interfaces provided a fertile ground for the discovery and manipulation of extraordinary physics, such as superconductivity [2][3][4][5], magnetism [6,7], magnetoelectric coupling [8,9], Rashba spinorbit coupling [10], persistent photoconductivity [11,12], and integer/fractional quantum Hall effect [13,14]. Over the last decade, leveraging these phenomena towards various devices, such as transistors [15][16][17][18][19], diodes [20], gas sensors [21], spintronic devices [22,23], and memory devices [24][25][26][27][28][29], has drawn considerable attention. In addition to the exotic phenomena listed above, the emergence of a high sheet density of electrons (typically 10 12 ∼10 15 cm −2 ) between two insulators is already attractive for some devices, such as in the role of channels or back electrodes.…”

“…The use of amorphous oxide on single crystal oxide substrates [16,24,30,31,[64][65][66][67][68] (Figure 1B) lowered the oxide deposition temperatures to <300 °C and expanded the deposition methods to ALD. The use of amorphous oxides deposited on polycrystalline oxide [17,21,25,32,33,69], which we term "All-ALD 2DEGs", provides a great advantage towards scalability and integration with existing and future technologies (Figure 1C). We note that significant progress has been demonstrated in MBE-based integration of epitaxial oxide 2DEGs systems with silicon [70][71][72] and other semiconductors [73,74].…”

SnO2 -SiO2 1D Core-Shell Nanowires Heterostructures for Selective Hydrogen Sensing

“…2 Therefore, it is essential to monitor the leakage of hydrogen at trace levels. [3][4][5] SnO 2 is one of the most reported n-type semiconducting metal oxide (SMOX) employed in chemo-resistive gas-sensing, due to its wide band gap (3.6 eV at 300 K), low material cost, fast response, stability and simplicity. [6][7] However, SnO 2 -based gas sensors are limited by their low selectivity, e.g.…”